Background: Despite the demand for cancer genetic services, patient-derived benefits remain poorly captured due to a paucity of validated tools. The Genetic Counselling Outcome Scale (GCOS-24), a genetics-specific Patient Reported Outcome Measure (PROM), has been adapted to evaluate our local cancer genetic service (CGS). We aim to evaluate the psychometric properties of GCOS-24 using Rasch analysis. Methods: 155 patients who attended CGS at National Cancer Centre Singapore (May 2016-2017) were recruited. The questionnaire was interviewer-administered pre- and post-counselling. Responses were subjected to Rasch analysis, comparing individual Rasch item scores pre and post. Multiple regression analysis was used to assess the association of baseline characteristics with changes in scores. Results: GCOS-24 questionnaire displayed good precision (person separation index > 2.0) and targeting (difference between person and item means < 1.0). Cognitive Control [post-intervention: median 1.23 (IQR -0.3-6.2); pre-intervention: median 0.46 (IQR -1.1-3.6)] and Emotional Control [post-intervention: median 0.99 (IQR -1.1-6.4); pre-intervention: median 0.61 (IQR -1.1-3.9)] scores showed significant improvement. All components of cognitive control consistently showed improvement. Notably, aspects of Emotional Control such as alleviating feelings of being upset (p = 0.88) and hopelessness (p = 0.2) did not reflect significant improvement. Family history (p = 0.047) and genetic testing (p = 0.002) were significantly correlated with cognitive control. As for emotional control, genetic testing (p = 0.002) and the female gender (p = 0.033) were also significantly correlated. Conclusions: This study shows that GCOS-24 is well adapted and validated in our population. Significant improvements in cognitive and emotional control are concordant with previous adaptations, demonstrating the value of empowerment through genetic counselling. This study highlights the need for further emphasis to be placed on improving hope and addressing emotions, through hope-based interventions and a systems-based approach to identifying and alleviating negative emotions associated with genetic conditions and testing.